Conductivity Modulation of 3D‐Printed Shellular Electrodes through Embedding Nanocrystalline Intermetallics into Amorphous Matrix for Ultrahigh‐Current Oxygen Evolution

Scaling up commercial hydrogen production by water electrolysis requires efficient oxygen evolution reaction (OER) electrodes that can deliver large current densities (more than 500 mA cm−2) at low overpotentials. Here, a highly active and conductive shell‐based cellular (Shellular) electrode is developed through a strategy of embedding nanocrystalline Ni3Nb intermetallics into an amorphous NiFe‐OOH matrix. The tailor‐made laser remelting process enables the dispersive precipitation of corrosion‐resistant nanocrystalline Ni3Nb in large numbers. After in situ electrochemical activation in the self‐developed growth‐mode‐control electrolyte, the amorphous NiFe‐OOH nanosheets and nanocrystalline Ni3Nb are formed on the as‐printed Inconel 718. The conductive atomic force microscopy (C‐AFM) studies and density functional theory (DFT) calculations elucidate that nanocrystalline Ni3Nb can simultaneously enhance the conductivity and activity of the catalyst film. Additionally, a Shellular structure inspired by nature is designed, interestingly, its specific surface area keeps constant with increases in porosity. This design can result in a large surface area and high porosity but with less material cost. Using this electrochemically activated Shellular electrode for OER, a high current density of 1500 mA cm−2 is achieved at a record‐low overpotential of 261 mV with good durability. This development may open the door for large‐scale industrial water electrolysis. A hierarchical electrode of amorphous NiFe‐OOH nanosheets with embedded nanocrystalline Ni3Nb intermetallics is achieved through in situ electrochemical activation of the 3D‐printed Inconel 718 metallic support with nature‐inspired conductive shell‐based cellular architecture. This tailor‐made electrode exhibits excellent electrocatalytic activity, high electronic conductivity, and good durability, enabling superior oxygen evolution reaction performance, especially at large current densities.